I'm going to try to understand what you were asking:
King of Sweden has 2 children, 1 boy, 1 girl.
Girl marries Crown Prince of Norway and they have one child, a son.
Swedish Boy dies without an heir. Would the sister's son be king to both the Norwegian and Swedish thrones?
Am I correct in my interpretation?
Ok, I'm going to state right away that I am venturing my guess... it's most likely not correct... but hey, I want to answer, so here I go:
In the Swedish Act of Succession, Article 8, it says that "A prince or princess of the Swedish Royal House may not become the sovereign ruler of a foreign state whether by election, succession, or marriage without the consent of The King and the Riksdag. Should this occur, neither he nor she nor their descendants shall be entitled to succeed to the throne of Sweden."
http://www.riksdagen.se/english/work/fundamental/succession.aspIn Article 10 of the Norwegian Constitution, is says, "The King shall reside in the Realm and may not, without the consent of the Storting, remain outside the Realm for more than six months at a time, otherwise he shall have forfeited, for his person, the right to the Crown.
The King may not accept any other crown or government without the consent of the Storting, for which two thirds of the votes are required. "
http://odin.dep.no/odin/engelsk/norway/system/032005-990424/index-dok000-b-n-a.htmlSo in a few words, I'll say it's highly unlikely. The daughter who married the Norwegian Crown Prince would be in line before her son, unless she signed away her succession rights at the time of her marriage, which would be more likely. That would mean her son is ineligible for the throne of Sweden also. But I will say that a King/Queen who has no children usually has an heir lined up in the event of their death... a brother, sister, or other eligible family members. Like Nicholas II's named heir was his brother George (until his death in 1899) and then brother Micheal (until Alexei's birth in 1904). But anyway, since his sister was his heir, it would be also unlikely that she would have been allowed to marry the Crown Prince of Norway until her brother had legitimate children of his own.
Does this make any sense?
